Ink industry has a broad market and various varieties. But in terms of technical performance, printing adaptability and application performance have an important impact on printing process and printing quality. Ink fineness is one of the main factors affecting the performance of ink and printing adaptability. Fineness will affect the gloss of the ink film and the rheology of the ink. Ink fineness refers to pigment, filler and other solid powder dispersion in the binder. Ink fineness and solid powder fineness is different, the latter refers to the basic of powder particle size, which generally pigment particle size less than 1, actually paint together with a number of fundamental particles adhesion state of aggregation (size can be up to 50), add the links to the ink material, after grinding, disperse aggregation and the good dispersion, the smaller the ink particles (fineness). General ink fineness is about 15, especially fine up to 1 ~ 2. The smaller the fineness of the ink film gloss and ink rheology is better.
Because the ink has a very rich color and the color of the vividness requirements are relatively high, the main use of grinding equipment for: Sand Mill.
After the formulation and dispersing equipment are determined, the grinding efficiency can be improved by adjusting the grinding medium, and the fineness of the ink can be controlled to obtain the ideal quality of the ink.
1. Experimental Facility
60L horizontal sand mill
2. Experimental Materials
(1) Ink Base Formula
(2) Dispersion Media:
Glass beads and zirconia beads with different particle sizes
(3) Experimental Process:
According to the formula, the raw materials are accurately matched into the base material, which is pre-dispersed evenly by the high-speed dispersing machine and then sent to the sand mill for grinding and dispersing. When the base material is ground in the sand mill, the first grinding speed is 500kg/2h, and the grinding speed is 500kg/3h from the second to the fineness qualified.
Ⅱ. Result And Discussion
1. The Effect of Grinding Media on Ink Fineness
Glass beads and zirconia beads of the same volume with a diameter of 2.0 ~ 2.5 ITIiTI are used to grind and disperse the base material, and the results are shown in Table 2.
2. Volume Ratio of Grinding Media to Base Material
In the process of sand grinding, in theory, the volume ratio of solid sand and grinding base material is 1:1. Under normal circumstances, the accumulation coefficient of sand is 0.639, the accumulation volume of sand and the volume ratio of abrasive material is 1.56:1, and the proportion of sand in the total sand mill is about 60%. In fact, according to the data in Table 3, when the grinding medium accounts for 70% of the total sand mill, the grinding effect is better.
This is mainly because of the large oil absorption of carbon black powder, the adsorption of the base material to alleviate the impact of sand stress action, thus delaying the whole dispersion effect. When the accumulation fraction of sand particles in the sand mill is slightly higher, the mixture of sand base slurry begins to appear expansion flow, which affects the dispersion efficiency. On the contrary, when the volume fraction of sand-grinding medium is too low, the gap between two adjacent sand grains will be increased, resulting in excessive loss of shear action, so that the grinding efficiency will decrease significantly.
3. Effect of Bead Size on Grinding Efficiency
There are two points to consider when choosing a bead size. First, it must be convenient to separate the grinding medium from the base material. As a general rule of thumb, the size of the grinding ball selected should be at least 50% larger than the mesh size at the outlet of the grinding chamber. The second is to get higher research ripple efficiency. The glass beads with diameters of 2.0 ~ 2.5 iTIITt and 3.5 ~ 4.0 iTIITt were used in the experiment.
Although it is shown in many data that mixed bead size has no special advantage in grinding, it can be seen from experiments that more ideal grinding results can be obtained when appropriate bead combination is selected. In fact, in the pre-dispersed base material, the diameter of pigment polymer is uneven. After the selection of beads with different particle sizes, the action stress of smaller and higher pigment polymer is different. In a short time, the pre-dispersed body is ground to a certain uniform fineness of the base slurry, thus improving the grinding efficiency.
Through the above industrial experiments and data analysis, it is very clear that the grinding efficiency of ink base material, after the formulation and equipment are finalized, the volume ratio of the grinding medium can be adjusted, and the selection of different sizes of beads in a certain proportion to improve the grinding efficiency. Experiments show that the content of acrylic ink is 10% carbon black powder in the horizontal sand mill using about 70% of the volume of grinding medium, particle size of 2.0 ~ 2.5 and 3.5 ~ 4.0 ratio is 4: At 1, the grinding efficiency of the grinding medium is the highest. For different ink, the best grinding medium system suitable for the ink can be found through experiments, so as to get higher grinding efficiency.